Abstract: The present invention relates to control of synchronous machines. A sensorless control system for an electrical machine is provided comprising a rotor and a stator having one or more phase windings for generating a rotating stator magnetic field. The current in the phase windings is monitored to determine real and imaginary components of the current vector in a rotating reference frame, from which real and imaginary components of the emf vector rotating in the rotating reference frame can also be determined. The ratio of the real and imaginary emf components is calculated, and an angular position of the rotational emf vector is estimated from this ratio. An angular error signal indicative of the deviation of the estimated angular position from a desired position in line with the real axis of the rotating reference frame is determined, and the machine is controlled such that the error signal tends towards zero.

Abstract: A flux switching electric motor (102) is disclosed. The motor comprises a rotor (104), a stator (106), field windings (124, 126) and armature windings (128, 130). #A microcontroller (134) controls supply of electrical current to the field and armature windings. A rotor position sensor includes a divider for (i) receiving an input signal dependent upon the rate of change of current in at least one field winding, (ii) receiving an input signal dependent upon the voltage across at least one armature winding, current through which causes at least part of the current in the field winding, and (iii) providing the microcontroller (134) with a control signal which is dependent upon the ratio of the input signals received by the divider.